Such magnetic field-sensitive sensors are known already. Such sensors for measuring lengths and angles are described in DE 32 40 794 C2 and in DE 39 26 328 A1. It is known from DE 38 29 390 A1 to use these magnetic field-sensitive sensors for measuring rotational speed.
As is known for instance from DE 296 14 974 U1, two sinusoidal signal tracks phase-shifted by 90° and a reference signal track exhibiting a single pulse are required for a sensor system.
So-called GMR sensors (i.e. Giant Magnetoresistive Sensors) have been used for quite some time as sensor elements. This technology is useful for highly integrative measurements of speed and position of objects. The high sensitivity of the sensor allows comparatively large distances between the measurement object and the sensor element.
The sensor composed of two Wheatstone bridges responds to field gradients in the sensor surface. The two bridges are adapted to the tooth structure such that two sinusoidal periods shifted by 90° are issued as output signals.
For scanning ferromagnetic tooth structures, the sensor requires a supporting magnet. In the most simple case, the supporting magnet is attached to the back of the sensor element. For difference measurement, the geometry of the individual bridge resistors is designed for one tooth spacing each. The tooth structure modulates the magnetic field of the supporting magnets by densifying or extending the magnetic field lines. This modulated field strength is converted by the sensor into a proportional electrical signal. The maximum output voltage of the sensor depends on the magnetic field strength of the permanent magnet, the distance between the sensor element and the measurement object, and the structure of the measurement object.
In DE 20 2005 011 361.1, a sensor has already been described, in which two GMR sensor elements were used. For optimizing the zero signal course, either the magnetic field source, the GMR sensor elements and/or the housing were tilted by a predetermined angle with respect to the reference plane of the scale at a given distance. Practice has shown that the adjustment of the respective tilt angle during production of the sensor is quite expensive.